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Topic: Transistor not fully turning off. (Read 2728 times) previous topic - next topic

Grumpy_Mike

If you think about it a transistor p = collector n = base p = emitter is still the same configuration of junctions when the emitter and collector are swapped.

What is different is only the geometry of the collector and emitter, with them swapped round the emitter is less efficient at emitting and the collector less efficient at collecting. The actual currents are in the same direction only the gain is very much lower.

SurferTim

@Grumpy_Mike: I have been thinking about it. I like reading your stuff, and value your technical expertise. That is why I asked you.

The collector and emitter were not my concern. I will presume zero current from collector to emitter. Does the base-emitter junction pass any current in this setup, or is it blocked? Normally (and you say this is kinda "normal") the base-emitter current could be enough to light a LED dimly.

Grumpy_Mike

Yes the base emitter is a diode like any other junction so if you mangle the connections you could get it either conducting current like a normal diode or if it is reverse biased there would be the reverse bias leakage, like a normal diode.
However, it is likely that the diode in this case would go into reverse biased breakdown and allow more current to flow thus lighting any in line LED.

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